1. Field of the Invention
This present invention relates to the technical field of quartz crystal microbalances and, more particularly, to a system for measuring resonant frequency and delay time of quartz crystal microbalance.
2. Description of Related Art
The quartz crystal microbalance (QCM), also known as an electronic nose, is generally used for measuring the micro substance. By pressing on the surface of a quartz crystal, some induction voltage will be generated on the surface of the quartz crystal. On the other hand, by providing voltage on the quartz crystal, the shape of the quartz crystal will be changed. The aforementioned reaction is so-called piezoelectric effect. The mass loading effect, published by the Sauerbrey in 1959, discussed about the reaction relation of the mass adsorbed on the surface of the quartz crystal and the quartz oscillating frequency. Therefore, the QCM generally uses to detect the variation of the oscillating frequency for determining whether the mass absorbed on the surface of the quartz crystal is changed or not. In addition, the QCM also can measure the absorbed level of the gas molecule generated by different absorbed materials for determining the type or the concentration of the gas. Therefore, the QCM generally applies to detect odor, gas, polluted material, or toxic gas. Especially, the development of QCM systems for use in fluids or with visco-elastic deposits has dramatically increased the interest towards this technique. Major advantages of the QCM technique used for liquid systems are that it allows a label-free detection of molecules. An example of the application areas of the QCM is shown on biotechnology field.
QCM composes of a quartz crystal and an oscillating circuit. The oscillating circuit is coupled to the quartz crystal for generating a resonant frequency of the quartz crystal. Because the surface mass loading variation of the quartz crystal is relatively small, the variation of the resonant frequency of the quartz crystal is also relatively small, therefore the resonant frequency and the surface mass loading should be measured more accurately. Thus, the conventional QCM cannot measure the variation of the resonant frequency accurately.
When the QCM begins to measure the oscillating signal, the amplitude of the oscillating signal generated by the quartz crystal will gradually increase to a predetermined value, and the frequency of the oscillating signal will also become stable. While the oscillating signal becomes stable, the conventional QCM begins to measure the frequency of the oscillating signal for counting variation of the oscillating signal and the mass cohered by the QCM.
In addition, the delay time will influence the character and the adsorption quantity of the material detected by the QCM, but the conventional QCM cannot measure the relation between the delay time and the material detected by the QCM. Therefore, it is desirable to provide a system for measuring resonant frequency and delay time of the quartz crystal microbalance to mitigate and/or obviate the aforementioned problems.